Short answers, pulled from the story.
Smeaton was the first person to call himself a civil engineer, coining the term to distinguish his work from that of military engineers trained at the Royal Military Academy at Woolwich. He founded the Society of Civil Engineers in 1771, which became the forerunner of the Institution of Civil Engineers established in 1818.
The Smeaton coefficient is a constant of proportionality describing how pressure varies inversely with the square of velocity for objects moving through air. The Wright brothers used it in their lift calculations, relying on a value of 0.005 before wind-tunnel experiments showed the correct figure was 0.0033.
Smeaton pioneered the use of hydraulic lime, a mortar that sets under water, and developed a technique of interlocking dovetailed granite blocks for the Eddystone Lighthouse built between 1755 and 1759. He drew on geology, meteorology, electrical research, and classical learning to design the structure, which remained in service until 1877.
When erosion of the underlying rock forced the lighthouse's retirement in 1877, the upper section was dismantled and partially rebuilt at Plymouth Hoe, where it is known as Smeaton's Tower. In 2020 a Cornish granite bust of Smeaton, sculpted by Philip Chatfield and funded by Trinity House, was installed in the tower's lantern chamber.
Smeaton built the Chimney Mill at Spital Tongues in Newcastle upon Tyne in 1782, the first five-sailed smock mill in Britain. He improved Thomas Newcomen's atmospheric engine, and the version he erected at Chacewater mine in Cornwall in 1775 was both the most powerful and most efficient steam engine of its time. He also adapted Denis Papin's diving bell design for underwater use at Ramsgate Harbour.
A memorial stone for Smeaton was unveiled in Westminster Abbey on the 7th of November 1994 by Noel Ordman, President of the Smeatonian Society of Civil Engineers. He is also depicted in the Stephenson stained glass window, designed by William Wailes and unveiled in Westminster Abbey in 1862, alongside five other civil engineers. John Smeaton Academy, a secondary school near Austhorpe in Leeds, is named after him.